This invention relates generally to gas turbine engines, and more particularly, to manufacturing bosses on cases of gas turbine engines.
Gas turbine engines typically include an engine casing that extends circumferentially around a compressor, and a turbine including a rotor assembly and a stator assembly. The rotor assembly includes at least one row of rotating blades that extend radially outward from a blade root to a blade tip.
The manufacturing of engine casings include the incorporation of areas in the casing wall where the thickness is significantly increased. These areas, known as bosses, can include two different types, outside diameter biased, where all the added thickness is on the outer surface of the casing, and neutral biased, where the is approximately an equal amount of material on the inside surface as on the outside surface of the casing. Allowances are made for these features during the manufacturing of the forgings, castings, or fabricated structures for these parts. These allowances result in significant amount of excess material that is removed during the manufacturing process.
This problem has been addressed by attaching OD biased bosses to casings using inertia/friction welding techniques to weld a cylindrical piece to the outside surface of the casing. However, because of limited access to the inside of the casing, this method cannot be used to add material to the inside surface of the casing.